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Commit 4ad5a321 authored by Roman Gushchin's avatar Roman Gushchin Committed by Tejun Heo
Browse files

cgroup, docs: document cgroup v2 device controller 



Add the corresponding section in cgroup v2 documentation.

Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: kernel-team@fb.com
Cc: cgroups@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent c2f31b79

Documentation/cgroup-v2.txt

+29 −4
Original line number Diff line number Diff line
@@ -53,10 +53,11 @@ v1 is available under Documentation/cgroup-v1/. 
       5-3-2. Writeback

     5-4. PID

       5-4-1. PID Interface Files

     5-5. RDMA

       5-5-1. RDMA Interface Files

     5-6. Misc

       5-6-1. perf_event

     5-5. Device

     5-6. RDMA

       5-6-1. RDMA Interface Files

     5-7. Misc

       5-7-1. perf_event

   6. Namespace

     6-1. Basics

     6-2. The Root and Views
@@ -1429,6 +1430,30 @@ through fork() or clone(). These will return -EAGAIN if the creation 
of a new process would cause a cgroup policy to be violated.





Device controller

-----------------



Device controller manages access to device files. It includes both

creation of new device files (using mknod), and access to the

existing device files.



Cgroup v2 device controller has no interface files and is implemented

on top of cgroup BPF. To control access to device files, a user may

create bpf programs of the BPF_CGROUP_DEVICE type and attach them

to cgroups. On an attempt to access a device file, corresponding

BPF programs will be executed, and depending on the return value

the attempt will succeed or fail with -EPERM.



A BPF_CGROUP_DEVICE program takes a pointer to the bpf_cgroup_dev_ctx

structure, which describes the device access attempt: access type

(mknod/read/write) and device (type, major and minor numbers).

If the program returns 0, the attempt fails with -EPERM, otherwise

it succeeds.



An example of BPF_CGROUP_DEVICE program may be found in the kernel

source tree in the tools/testing/selftests/bpf/dev_cgroup.c file.





RDMA

----